The artificial sweetener 4,1',6'-trichloro-4,1',6'-trideoxygalactosucrose ("sucralose") is derived from sucrose by replacing the hydroxyls in the 4, 1' and 6' positions with chlorine (In the process of making the sweetener, the stereo configuration at the 4 position is reversed--hence the compound is a galactosucrose.) The direction of the chlorine atoms to only the desired positions is a major synthesis problem because the hydroxyls that are replaced are of differing reactivity; two are primary and one is secondary. The synthesis is further complicated by the fact that the primary hydroxyl in the 6 position is unsubstituted in the final product.
This invention provides an improved route to sucrose esters wherein the ester groups are bonded to predetermined positions on the sucrose molecule. In one aspect, the invention provides an improved route to 4,2,3,3',4'-penta-O-acetylsucrose ("4-PAS") or 6,2,3,3',4'-penta-O-acetylsucrose ("6-PAS") or both, which can be employed to produce sucralose. 4-PAS is readily rearranged to 6PAS, which can be chlorinated and then deacylated to produce sucralose.